“It’s telling that the multinationals are taking this sanctions business very seriously and are preparing to pull out of Iran. That’s really crystallizing the loss of production we’re facing,” said John Kilduff, partner at energy hedge fund Again Capital.

An updated timeline on the restart of the Syncrude oil sands facility added a jolt of volatility into U.S. crude trading, said Kilduff.

In Canada, majority stakeholder Suncor said on Monday that some Syncrude production would come back online in July, sooner than expected. It will not resume full operations until September, however, which is later than expected.

The 360,000-barrel-per-day (bpd) facility in northern Alberta has been shut since late June, cutting oil flows into Cushing, Oklahoma, the delivery point for U.S. crude futures.

Stocks in Cushing rose slightly between Tuesday and Friday, according to market intelligence firm Genscape, according to analysts who saw the data. Cushing inventories hit a three-and-a-half-year low last week.

“Cushing is clearly screaming out for crude,” said Virendra Chauhan, oil analyst at consultancy Energy Aspects.

The tightness at Cushing and the potential increase in Gulf exports “both have implications for how quickly the prompt overhang in the market can clear, and thus provide some direction for prices,” Chauhan said.

The market has grown concerned that if the Saudis offset the losses from Iran, it will leave oil markets at risk of further production declines in countries like Venezuela and Libya.

“If the Saudis and others replace the losses from Iran, there will be basically no spare capacity left,” Societe Generale oil analyst Michael Wittner said.

Saudi Arabia, fellow members of the Organization of the Petroleum Exporting Countries (OPEC) and allies including Russia agreed last month to increase output to dampen price gains and offset global production losses in countries including Libya.

Libyan oil output has halved in five months, falling to 527,000 barrels per day (bpd) from a high of 1.28 million bpd in February, the head of the National Oil Corporation, Mustafa Sanalla, said on Monday.

“Tomorrow it will be less and the day after tomorrow less again. And we are going lower,” Sanalla said.

U.S. oil output is increasing but is unlikely to be able to fill the supply gap if U.S. sanctions are successful in blocking Iranian exports.

U.S. energy companies last week increased the number of rigs drilling for oil by five to 863, up 100 year-on-year, energy services firm Baker Hughes said on Friday. The U.S. rig count, an early indicator of future output, is much higher than a year ago as companies have ramped up production in response to higher prices.